1. Field of the Invention
The present invention relates to a sheet feeding apparatus, which feeds a sheet such as an original, and an image reading apparatus and an image forming apparatus including the same.
2. Description of the Related Art
In the past, there has been known an image reading apparatus including a so-called flow-readable original feeding apparatus (ADF) which automatically feeds an original to a predetermined image reading position and reads image information of the original by an optical system, which is disposed at the image reading position, when the original passes through the image reading position. In such an original feeding apparatus, a pickup roller feeds originals stacked in an original stack tray, and a separating unit separates the originals one by one and feeds the originals to a predetermined image reading position. Also, in order to inhibit an operator from setting an original and prevent conveyance failure upon two-sided reading, the pickup roller sets a position retracted upward as a home position, and the rotation of the pickup roller is performed by a pickup arm.
Herein, the pickup arm is rotated to a feeding position and a retracted position by a normal or reverse rotation of a driving unit. Therefore, for example, in order to rotate the pickup arm from the feeding position to the retracted position upon two-sided reading, it is necessary to provide a driving source different from a driving source which drives each conveying unit for reversing an original. Therefore, in the case of an original feeding apparatus capable of two-sided reading, two driving units are required, resulting in cost increase.
On the other hand, there is disclosed an original feeding apparatus in which when a spring member is engaged with a pickup arm and a driving of the pickup arm is interrupted, the pickup arm is rotated from a feeding position to a retracted position by a tension of the spring member (see Japanese Patent Laid-Open No. 2006-176290).
However, in the original feeding apparatus described in Japanese Patent Laid-Open No. 2006-176290, the spring member needs to be engaged with the pickup arm in a rotation area from the feeding position to the retracted position. Therefore, the action area of the spring member is long and the posture of the spring member is unstable, causing a variation in a tensile force. Therefore, it is apprehended that an original feeding force of an original feeding roller will be unstable. Also, an operation of hooking the spring member to the pickup arm occurs, and when assembling the pickup arm, the assembling is difficult.
Therefore, it is desirable to provide a sheet feeding apparatus in which a feeding roller can take a feeding position and a retracted position through a simple configuration, and an image reading apparatus and an image forming apparatus including the same.